/firebase-analytics

name: firebase-analytics
description: "Use when logging analytics events, setting user properties, configuring default event parameters, building funnels, or adding screen-view tracking."
license: MIT

Firebase Analytics Skill

This skill defines how to correctly implement Firebase Analytics in Flutter applications, covering setup, event logging, user properties, and data collection best practices.

When to Use

Use this skill when:

• Setting up and configuring Firebase Analytics in a Flutter project.
• Logging predefined or custom analytics events.
• Setting user properties or default event parameters.
• Implementing screen view tracking with GoRouter or Navigator observers.
• Building conversion funnels or tracking user flows.

---

1. Setup and Configuration

flutter pub add firebase_analytics
flutter run

import 'package:firebase_analytics/firebase_analytics.dart';

// After Firebase.initializeApp():
FirebaseAnalytics analytics = FirebaseAnalytics.instance;

• Initialize Firebase before using any Firebase Analytics features.
• Analytics **automatically logs** some events and user properties — no additional code needed for those.
• On iOS, if your app does not use the IDFA (Advertising Identifier), use the IDFA-free Analytics dependency (`FirebaseAnalyticsCore` under Swift Package Manager, or `FirebaseAnalytics/Core` under CocoaPods) instead of the default `FirebaseAnalytics` dependency to avoid App Store review questions about advertising identifiers:
• **Swift Package Manager:** set `FIREBASE_ANALYTICS_WITHOUT_ADID=true` when building (`FIREBASE_ANALYTICS_WITHOUT_ADID=true flutter build ios`).

Add Navigator Observer for Automatic Screen Tracking

MaterialApp(
  navigatorObservers: [
    FirebaseAnalyticsObserver(analytics: FirebaseAnalytics.instance),
  ],
);

For GoRouter, log screen views manually on route changes:

GoRouter(
  observers: [FirebaseAnalyticsObserver(analytics: FirebaseAnalytics.instance)],
);

Verification Checklist

1. Confirm `Firebase.initializeApp()` completes before accessing `FirebaseAnalytics.instance`. 2. Run the app and check the Firebase DebugView console for incoming events. 3. Confirm automatic events (`first_open`, `session_start`) appear without extra code.

---

2. Event Logging

Use **predefined event methods** when possible for maximum detail in reports and access to future Google Analytics features:

await FirebaseAnalytics.instance.logSelectContent(
  contentType: "image",
  itemId: itemId,
);

Use the general `logEvent()` method for both predefined and custom events:

await FirebaseAnalytics.instance.logEvent(
  name: "select_content",
  parameters: {
    "content_type": "image",
    "item_id": itemId,
  },
);

Custom Event Example — E-commerce Add-to-Cart

Future<void> logAddToCart(String productId, String productName, double price) async {
  await FirebaseAnalytics.instance.logEvent(
    name: 'add_to_cart',
    parameters: {
      'product_id': productId,
      'product_name': productName,
      'price': price,
      'currency': 'USD',
    },
  );
}

• Event names are **case-sensitive** — names differing only in case create two distinct events.
• Up to **500 different event types** with no limit on total event volume.
• Event names must start with an alphabetic character, contain only alphanumeric characters and underscores, and be no longer than **40 characters**.

---

3. Parameters and Properties

• Parameter names: up to **40 characters**, must start with an alphabetic character, contain only alphanumeric characters and underscores.
• String parameter values: up to **100 characters**.
• The prefixes `firebase_`, `google_`, and `ga_` are **reserved** — do not use them for parameter names.
• Up to **25 custom parameters** per event.
• Register custom parameters in the Analytics console to use them as dimensions or metrics in reports.

Set default parameters for all future events (not supported on web):

await FirebaseAnalytics.instance.setDefaultEventParameters({
  'app_version': '1.2.3',
  'environment': 'production',
});

Clear a default parameter by setting it to `null`.

---

4. User Properties

await FirebaseAnalytics.instance.setUserProperty(
  name: 'favorite_food',
  value: favoriteFood,
);

Set the user ID to correlate events across devices:

await FirebaseAnalytics.instance.setUserId(id: 'user_12345');

• Create custom definitions for user properties in the Analytics console before using them.
• Up to **25 custom user properties** per project.
• Use user properties for audience segmentation, report filtering, or A/B test targeting.

---

5. Best Practices

• **Request necessary permissions** before collecting user data, especially on platforms with strict privacy controls.
• **Never log** sensitive or personally identifiable information in events or user properties.
• Use **consistent naming conventions** (snake_case) for custom events and parameters.
• Group related events to track user flows and conversion funnels.
• Use **DebugView** in the Firebase console during development — enable it on a physical device with:
• **Android:** `adb shell setprop debug.firebase.analytics.app <package_name>`
• **iOS:** Add `-FIRDebugEnabled` to scheme arguments in Xcode.
• **Test** analytics implementation before deploying to production by confirming events appear in DebugView.

---

References

• [FlutterFire GitHub Repository](https://github.com/firebase/flutterfire)